Discussion on Safety Design of Wind Turbine Bolts
Bolted joints are an important assembly method in wind turbine assembly and involve almost all components of a wind turbine. Therefore, the selection and strength check of bolts is an important guarantee for the reliability of wind turbines.
With the leap-forward development of China's wind power industry, along with the continuous decline in wind power generation costs, the price of wind turbines is getting lower and lower, and the price wars of major wind power equipment assembly enterprises have already reached a stage of white-hot. How to ensure the quality of wind turbines under the condition of reducing costs has become an important issue for major wind power enterprises. As an important link of wind power equipment, bolts are one of the main difficulties in reducing the cost of wind turbine design due to the uncertainty of its characteristics.
1. Current status of bolting
At this stage, the problem of bolt failure in China's wind turbines has been reflected in the high-strength bolts that connect the tower flanges. The main failure modes are: the phenomenon of slipping, twisting, yielding, and even breaking when the wheat grabbing belt is installed; bolt breakage occurs during the operation of the equipment, which threatens the operation of the unit, and even causes the wind turbine to collapse. Wind power equipment
The reason for these problems in tower high-strength bolts is that the theory and experience in the design process cannot be ignored, except for the unqualified quality of the bolts themselves.
2. The main way of bolt checking
At this stage, people mainly design and check the reliability of bolts by using finite element software analysis and scientific calculation.
In the process of using finite element software for analysis [1], we can achieve the preload force loading by direct loading method, equal efficiency method, equivalent strain method and equivalent temperature method. However, these loading methods may not transmit shear stress, or may not simulate the friction behavior of the bolt and the joint in reality, and the preload force loss caused by loosening of the nut cannot be considered. As a result, the bolt stress generated during the actual finite element simulation process is too large, and therefore, it is generally not used as a means for checking the bolt structure of the wind turbine.
